1. Field of the Technology
The present application relates generally to wireless communication networks for mobile stations, and more particularly to methods and apparatus for controlling wireless network resources for data sessions based on IP address usage.
2. Description of the Related Art
A wireless communication device, such as a mobile station operating in a wireless communication network, may provide for both voice telephony and packet data communications. A mobile station may, for example, be compatible with 3rd Generation (3G) communication standards (such as cdma2000) and utilize Global System for Mobile Communications (GSM), Time Division Multiple Access (TDMA), or Code Division Multiple Access (CDMA) wireless network technologies.
In a cdma2000™ based wireless network, a mobile station sends and receives packet data during a Point-to-Point Protocol (PPP) session established with a Packet Data Serving Node (PDSN). The packet data could be e-mail, web browser, news and weather data, as a few examples. When an idle mobile station has packet data to send, it initiates a new PPP session with the PDSN. The mobile station may also be directed by the network to initiate a PPP session when the network has data to send. During initialization of the PPP session, an IP address from a pool of IP addresses managed by the network is dynamically assigned to the mobile station This assignment may be performed by the PDSN during an Internet Protocol Control Protocol (IPCP) stage in a Simple IP network as defined in IS-835. In a Mobile IP network, the network assigns an IP address as part of Mobile IP registration.
Once PPP connectivity is established between the mobile station and the network, it is generally maintained even when no data is being communicated. The packet data service at the mobile station and network is assumed to have entered “dormant” state in such case. To reduce latency in exchanging application level data (e.g. to ensure quick data availability for an always-on mobile station), it is desirable for the PPP session to be maintained continuously even during periods of communication inactivity. The PPP session may be closed by the PDSN, however, when there is communication inactivity for some relatively long period of time and the mobile station is unavailable.
For this purpose, the PDSN maintains a data inactivity timer for each mobile station involved in a PPP session. The exact behavior depends on whether the network and the mobile station have a Simple IP connection or a Mobile IP connection. In a Simple IP network, this timer may be passed to the mobile station in the form of maximum PPP inactivity timer. This data inactivity timer is set to an initial value (e.g. 2 hours) and is reset for each occurrence of communication activity. If no packet data is sent or received for the mobile station over the time period defined by the data inactivity timer, the PDSN sends a Link Control Protocol (LCP) Echo-Request message to the mobile station. If there is no response to the LCP Echo-Request from the mobile station within the time period defined by data inactivity timer, the PDSN closes the PPP session. The PDSN closes the PPP session as it infers that the mobile station is no longer available for communication. In a Mobile IP network, the network can specify a Registration lifetime for a Mobile IP connection If the mobile station does not re-register within the network specified lifetime, the PDSN closes the PPP session.
The above-described procedure is useful since it helps release network resources to make them available to newly-arriving mobile stations. For example, the pool of IP addresses is finite and limited—if the entire pool of IP addresses are assigned, the PDSN does not have any available IP addresses to assign to newly-arriving mobile stations. In addition, the network also maintains information about the binding of the IP address to a mobile station which requires memory.
A problem arises, however, in the selection of a suitable initial value for the data inactivity timer. If network operation is very busy (i.e. there is a relatively large number of always-on mobile stations operating in the wireless network), a data inactivity timer with a relatively large initial value will not provide for the expeditious release of network resources for newly-arriving mobile stations. If network operation is very slow (i.e. there is a relatively small number of always-on mobile stations operating in the wireless network), a data inactivity timer with a relatively small initial value will result in numerous unnecessary attempts to release network resources and a resulting inefficient use of bandwidth. In addition, the data inactivity timer may also be selected by the network based on the quality of service (QoS) subscribed to.
Accordingly, what are needed are methods and apparatus for controlling wireless network resources for data sessions so as to overcome the deficiencies in the prior art.